An antenna device includes a housing having a lower portion for coupling to a non-magnetic option coupler of a vehicle, an insulating member engaged in an upper chamber of the housing, a conductor member engaged into a central bore of the insulating member for engaging with the non-magnetic option coupler, a conductive coupling element having a lower portion engaged into the housing, and a coaxial radiating assembly includes a coaxial radiating device having a central radiating member for connecting to the conductor member, and a peripheral radiating member for connecting to the conductive coupling element, and an insulating element mounted between the central radiating member and the cylindrical radiating member.